Labels – O
- O-CETERA
- OA2 Records
- Oberlin Music
- Oblique Sound
- Oboe Classics
- Obsessions
- Ocora
- Ode Records
- Odin
- Odin Records
- Odradek Records
- Oehms
- Off
- Ogun Recording Ltd.
- Ohrwurm Records
- Okeh
- Olde Focus Recordings
- Olufsen Records
- Olympia
- Olympic Records
- Omnivore Recordings
- On the Corner
- OnClassical
- Ondine
- One World Records
- ONJ Records
- Onjazz Records
- Onyx
- Opening Day
- Optical Substance Productions
- Opus 3
- Opus Arte
- Orchid Classics
- Organ Promotion
- Origin Classical
- Origin Records
- Original Jazz Classics
- Orlando Records
- Oslo Session Recordings
- OTA Records
- OUR Recordings
- Out Here
- Out Of The Past Music
- Outhere
- Outnote Records
- OUTSIDE MUSIC
- Ozella Music
- Ozit Morph Records